Measuring plant lighting

chazbolin

Well-Known Member
I have enjoyed many spirited discussions with members on this and other forums re the way plant lighting systems are field measured and how manufacturers publish their lamps output data. As a direct result of these discussions I recently was asked to help contribute to a paper that proposes how manufacturers might consider publishing their lamp's outputs in a format that identified output in the the three peak photosynthetic absorption regions. Think of it as like an N-P-K system for rating plant lighting.

In developing this document we used manufacturer data that was available at the time of this publication from a variety of manufacturers websites. Nothing in this document is meant to construe that we are suggesting that any one technology is better than the other. Our interest in developing this document was to simply present another way of viewing how artificial plant lighting can be represented in a way that does not confuse the gardener with information and values that may be mostly irrelevant when it comes to selecting the best lamp for their needs.
I think a comparison of the technologies as detailed within this documents 5 most common specification techniques implies that by relying on the numbers alone you can be left with a sense of one technology is 'better than another' for occupying that coveted space above our garden. However a closer analysis of the data reveals that if you've actually grown with the supposed 'superior technologies' plant response is dictated by forces greater than just a mfg claiming 'my number is bigger than yours so it must be better' type of marketing mentality. Which simply reinforces my belief, that at the end of the day, it will always comes down to plant response which does in fact, trump many of these claims.

http://www.inda-gro.com/pdf/MeasuringPlantLight.pdf
 

sheldonblack

Active Member
I have enjoyed many spirited discussions with members on this and other forums re the way plant lighting systems are field measured and how manufacturers publish their lamps output data. As a direct result of these discussions I recently was asked to help contribute to a paper that proposes how manufacturers might consider publishing their lamp's outputs in a format that identified output in the the three peak photosynthetic absorption regions. Think of it as like an N-P-K system for rating plant lighting.



I think a comparison of the technologies as detailed within this documents 5 most common specification techniques implies that by relying on the numbers alone you can be left with a sense of one technology is 'better than another' for occupying that coveted space above our garden. However a closer analysis of the data reveals that if you've actually grown with the supposed 'superior technologies' plant response is dictated by forces greater than just a mfg claiming 'my number is bigger than yours so it must be better' type of marketing mentality. Which simply reinforces my belief, that at the end of the day, it will always comes down to plant response which does in fact, trump many of these claims.

http://www.inda-gro.com/pdf/MeasuringPlantLight.pdf


I don't like readin much, that's why I bought a light intensity meter.
 

hyroot

Well-Known Member
That's chart at the end is inaccurate . For example. The only digital cmh that exist pull 315 watts. There is no 6500k cmh nor one that pulls 1100 watts. The highest watt cmh I know of is 860. Even the DNA 900 w cmh is the Philips 860w rebranded. Inda gro is very biased. Not to say anything about the lights them selves. Just the b.s. Comparisons to other lights. Earlier videos Darryl made, he stated led can't stand up to induction. After psuagros led vs ig grow, led of half the watts killed the ig. Darryl then developed the led pontoon. Again nothing against the lights them selves. That then contradicted what he had said prior. Car salesmanship....
 

Bumping Spheda

Well-Known Member
Interesting concept, imo. One thing that can't really be taken into account, though, is plant species and desired photo morphology of the plant. Not everyone wants, or can deal with tall indoor plants.

But, assuming we wanted plants that looked and behaved as similarly to outdoor plants as possible, would it be safe to say that -excluding UV and IR output- the closer a light source resembles the blackbody locus of the desired CCT the better the light source will be for growing?

vz32.jpg

The halogen with dichroic coating is basically identical to the spectral distribution of a 2700k blackbody. Within the visible spectrum, and efficiency aside, is that not "perfect"?

With that in mind, CCT coupled with an accurate CRI measurement seems to actually be a pretty good indication of spectral output. With those values in check, a PAR measurement seems to mean a lot more to me.
 

tags420

Well-Known Member
Hate is a strong word, but I really really really don't like this...

Where to begin...even in the document they say you still need a quantum meter(par umols) and still need to look at the spectral charts. Then what's the point? and it doesn't show intensity.

Photosynthesis takes photons(measure in umols from a quantum meter, not par meter) and co2 then converts them into glucose and O. Spectrum makes more of the photons available...but there is still only the fixed amount put out by the light. And if that is not enough to produce good growth, then no matter what your spectrum is there is not enough.

The point of efficient lighting is that we can output(umols) more, while using the same or less power draw(watts). Meaning the term watt is useless to describe what is coming out of a region(VCF).
FOR EXAMPLE
2 lamps with identical VCF region and identical spectrums and identical wattages.
Light #1
CENTER:1000umol
2x2avg:500umol
4x4avg:300umol
Light#2
CENTER:600umol
2x2avg:300umol
4x4avg:150umol
But when using your system the better light(light#1) is hidden because you won't accept the value and importance of PPFD...of even just PPF so that is can be universal for all light sources. But because led are a directional source PPFD is a better measurement of what will actually be getting to the canopy.

PPF/region is closer to something useful.

All we need to know a ppfd umol footprint graph from the recommended height, see the spectral chart, and the wattage pulled to do it all. With those we can make perfectly informed decision that will show the true performances and capabilities of any light, from any source/company/technology.
 

chazbolin

Well-Known Member
In response to Hyroot and Tags, I had expected some brisk debate due to the large amount of information this document represents and I have not been disappointed. I did however think that there might be a day or two of digestion before the bullets would fly.

Let me start off by saying that I am not going to get in a pissing match or let it ever get personal when comments are directed at me or Inda-Gro. This thread is not about Inda-Gro or any personal animus you might have with them. The document itself is to be considered a work in progress. If you don't like what is in it, don't read it. But a lot of work has gone into this and for anyone to suggest that the document is irrelevant or that the data is skewed or biased does not have a full appreciation for what it represents.

What V-C-F does represent is the raw power the lamp produces in the three absorbance regions based on manufacturers published spectral distribution graphs. We plotted each lamp @ 301 lines which requires a mathematical summation of the spectral distribution graph on a nanometer by nanometer basis. It's completely unbiased and pure math. Nothing more. Is it perfect? No. We admit to that several times within the article. It is just data to be taken and interpreted by those reviewing it. As you can see for yourself that based on these 5 metrics nothing in this document promotes Inda-Gro as exceptional. If anything LED is given the highest marks under these metrics which is by their own designs, the intent of LED mfg's.

The issue Hyroot has with 1000 watt CMH data is a result of us plotting the 1000 watt Eye Hortilux Blue which is defined as you properly noted is a metal halide but the spectral distribution certainly lends itself to a plasma/incandescent/sunlight distribution more so than any other metal halide that we were aware of and that's why we chose it. To us the spectral distribution graph that Hortilux provides makes it look like a ceramic metal halide. If you know of any other metal halide that produce this relatively smooth continuous broad band distribution I would like you to point to it. For now we're going to leave it as it is driven on an electronic ballast. However for clarity the next update will include the 400 watt CMH running mag ballasts.

http://www.eyehortilux.com/products/metal-halide/SystemReqs/mt1000b-dhorhtl-blue/57945

Darryl has about 15 LED panels that they have tested in various gardens. They have zero bias against SSL and to my knowledge have never stated publicly or privately that LED does not have it's place as an alternative to HID. The Pontoon was added to enhance flowering by emitting a 660nm wavelength at lights on and a 730nm wavelength at lights out. You don't have to use it to flower but I believe for cash crops the value in adding it as it's ROI represents a 1/2 crop cycle I think it does make sense. I don't care what you grow with or what your personal preferences are. None of this is about that.

Tags what is to hate about all this is that it IS difficult to understand lighting and plant lighting in particular. I've never said there is no value to PPFD it's just a value to field measurement. For example: If you know the area of coverage and the required PPFD then multiply those values you'll get the needed PPF. Now you look at the lamps rated PPF and you can determine how many lamps you're going to need. Than you need to look at your layout and make judgement calls based on metered PPFD readings at the canopy. So while you can fairly easily go from a PPF to PPFD it's impractical due to the wide variables that mfg's could standardize PPFD values when it's ultimately determined in the field.

The easiest way I correlate this is to remind folks that area lighting lamps are specified in lumens not footcandles or lux. To specify a grow lamp in PPFD would be akin to specifying an area lamp in lux or foot candles with a candela plot. If you must promote PPFD as a standard then you should propose a standardized 'candela type' plot plan for the grow lamp industry. And when that has been adopted you still will not have a numerical value to spectral distribution in the the three absorbance regions the lamp should emit for that species. And to your point about publishing PPF values if you go to section 2 of the spread sheets we did do this as a total PPF, as a uMoles/s/region and a % of each region for that total.

If you need further proof that this is a complex topic I will point you to a well known company that produces PAR quantum meters that consistently mistakes PPF and PPFD values. These statements are on there site and they do not distinguish the differences between PPF and PPFD in that they provide all values in PPFD. I won't name them, but I think you own one, whereby these are comments picked up directly from their site and they imply by these statements there is no difference between PAR, PPF and PPFD. Go figure there is confusion in the industry.

Measure photosynthetically active radiation (PAR, PPF, PPFD) from the sun or electric lights in μmol m[SUP]-2[/SUP] s[SUP]-1[/SUP]

Photosynthetically Active Radiation (PAR) is also called the Photosynthetic Photon Flux (PPF) or Photosynthetic Photon Flux Density (PPFD) and the units are μmol m[SUP]-2[/SUP] s[SUP]-1[/SUP] (micromoles of photons per meters squared per second).
Bumping Spheda: If we're going to artifically recreate sunlight spectrums we're going to give up efficiencies which would make it impractical, ie halogens/incandescents. As far as near perfect Kelvin it would not be 2700 Kelvin but I believe would instead be a lamp emitting, the sun is itself a black body radiator, between 5000-6500 kelvin on the surface of the planet.

You have defined the challenge in that we're looking to find the right lamp that is efficient enough to make it economically feasible (it'll never be a black body model) by producing adequate intensities and spectrums for optimum plant response in a controlled environment. And it is to that end we continue to strive.
 

hyroot

Well-Known Member
Well cmh has a ceramic arc tube and mh have a quartz or aluminum arc tube. The ceramic arc tube is more resistant to corrosion and has a better and more even distribution of light. Cmh lasts twice as long with less degrading than mh. Cmh runs 2-3 times cooler in temp than mh. All cmh has far more red and deep red than the hortilux blue. Also cost half as much and run less watts. Calling a hortilux blue a cmh would be like saying a t5, t8, or t12 bulbs are induction bulbs.

so no go there my friend.
 

Loonquawl

Well-Known Member
Photosynthesis takes photons(measure in umols from a quantum meter, not par meter) and co2 then converts them into glucose and O. Spectrum makes more of the photons available...but there is still only the fixed amount put out by the light. And if that is not enough to produce good growth, then no matter what your spectrum is there is not enough.
Could one measure the amount of CO2 a plant absorbs over a certain amount of time and compare different spectrums in a controlled environment?

Or measure the amount of light that is reflected (not absorbed) by the plant? If you could do this, maybe you could program an LED array to change the light spectrum as needed at any given time.
 

hyroot

Well-Known Member
Could one measure the amount of CO2 a plant absorbs over a certain amount of time and compare different spectrums in a controlled environment?

Or measure the amount of light that is reflected (not absorbed) by the plant? If you could do this, maybe you could program an LED array to change the light spectrum as needed at any given time.


yes to all that. I can't recall the name of the devices they use. But if you google it in oxford journals experimental botany. There are plenty of studies. Where they measure the amount of co2 and o2 exchange on the surface of the leaf and well as light on the surface of the leaf. I posted a link quite a few times in various threads where they do just that. I'll look for it and post it

edit: found it

http://pcp.oxfordjournals.org/content/50/4/684.long

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892149/
 

tags420

Well-Known Member
You and I have discussed this a few times before so that's why the bullets are flying quick...gun was already loaded.

Your right, PPFD is a field measurement. I agree that PPF is the equal and unbiased way to show what I am talking about.

I may have misunderstood the way w/region is calculated.
So say looking at a spectral chart and a blue is peaking 450nm with 1500mW/m2...is that what is converted to your w/region? and then also the value in mW/m2 for 300 other different nm's too? If so, that is something I can get behind. I need to know more
 

chazbolin

Well-Known Member
I may have misunderstood the way w/region is calculated.
So say looking at a spectral chart and a blue is peaking 450nm with 1500mW/m2...is that what is converted to your w/region? and then also the value in mW/m2 for 300 other different nm's too? If so, that is something I can get behind.
You're getting closer! Lose the M2 since we're not dealing in area just uMoles/s of the 301 slivers of the spectrum and present it in 5 different formats within the spread sheets. Future updates will show the formulas used to plot each of these categories.

I sense a convert coming in the door...loading up the pipe as we speak
 

tags420

Well-Known Member
We have had at least 4 pages of debate about this throughout different forums...could have helped me along faster. Did that IG link/article just become available?

I still like PPF. Just because it is easier for gardener/users to interpret and use practically. Such as DLI and canopy intensity requirements. There is some difficult math to get mW/m^2/nm in to a understandable photon value that correlates with plant growth.

But your system has some good merit behind it that I didn't see at first. Hell you and I have been discussing it for about 3 weeks now. I have said it before...PPF/region and you have a deal with me.

EDIT: since you edit I will...your first comment was better.
How do you measure without m2. Is that in a sphere like ppf?
 

chazbolin

Well-Known Member
Thank you Tags. That means a lot to me.

The reason I was not willing to go on record with this is earlier is that there are many more points I wished to address in this paper. IG has kept an open mind and financed the project that if you review the data as it's been presented has not been a ringing endorsement of their products. What intrigued me is this method of watts/region is as easily understood as brake horsepower measured at the rear wheels not at the engine. What I found equally of interest though is how some of the emerging technologies, such as plasma, might lose some of their arguments when comparing plasma with alternative technologies especially when you include the need for a 1000 watt DE HPS to complete a cycle when using plasma. But I'm sure the response from 'some major plasma company will be forth coming and I do await the opportunity to engage in that debate.

I think the one thing that all of this work continues to remind me of is that the ultimate authority on whether or not the 'right lighting' is being used will be plant response. And on that point I think we can all agree.
 

chazbolin

Well-Known Member
EDIT: since you edit I will...your first comment was better.
How do you measure without m2. Is that in a sphere like ppf?
It does not take an integrating sphere to develop these values. It's a mathematical summation of each individual wavelength broken into these 3 regions. If anything the LED guys should be buying me drinks when pointing to the technical comparison spreadsheets.
 

tags420

Well-Known Member
But how are those values achieved is my question? A spectroradiometer graph is taken at a distance and expressed in mW/m^2/nm. I am not arguing...just trying to clearly understand.
 

Bumping Spheda

Well-Known Member
As discussed in the paper, couldn't V-C-F be fooled just as CFL (and now LED) manufacturers cater phosphor mixtures to the CRI standard? Just because a light has a respectable looking V-C-F doesn't necessarily mean it hits photosynthetic efficiency peaks very well at all. It's similar to how an 80 CRI 2700k LED might have an embarrassingly low R9 value. And if even if it hits the nail on the head as far as a PS efficiency peak is concerned, if that's all it hits, is that optimum? This would be related to broad band coverage and any potential benefit that might provide plants.

So, given a V-C-F measurement I still need a spectral analysis graph. What does V-C-F even tell me apart from a numerical breakdown of the spectral analysis graph clumped into three groups? Wouldn't radiant efficiency and a spectral analysis graph do me just as well?
 

chazbolin

Well-Known Member
But how are those values achieved is my question? A spectroradiometer graph is taken at a distance and expressed in mW/m^2/nm. I am not arguing...just trying to clearly understand.
You don't need an integrating sphere to develop V-C-F. These values are achieved by knowing the lamps spectral distribution and factoring consumed watts verses it's efficiencies into turning electricity into plant usable light.

As a grow lamp mfg I might use an integrating sphere to easily determine PPF output. For general area lamp applications I would use it to determine a lamps lumen output. As an area light fixture mfg I would want an in situ value from an integrating sphere in lux/footcandles.

As a grow light fixture mfg however I would not be interested in area sphere data since they are for starters photopically corrected for human visual luminosity function. The area readings that a sphere gives you are designed for candela plot plans and are photopically adjusted. Furthermore they are providing intensity not spectrum in a numerical value. With plants you would want to know those intensity values in the 3 peak absorption regions and totaled as a PPF/s/total or PPF/s/region value which can be accomplished mathematically, as we have done on pages 6-7 of the charts, to provide the gardener with information that is unique to determining available energy within the regions of plant photosynthetic requirements.

So, given a V-C-F measurement I still need a spectral analysis graph. What does V-C-F even tell me apart from a numerical breakdown of the spectral analysis graph clumped into three groups? Wouldn't radiant efficiency and a spectral analysis graph do me just as well?
correct you would still want to identify where in those regions the light was emitting. You would also want to ideally see spectral distribution that is unique to the plant species being grown indoors and try to match it. V-C-F is expressed in radiant energy as an absolute and a % of PAR regions as one of the 5 techniques we used on page 6-7 of the document.

What V-C-F does is provide the grower with a way of seeing what is shown on a spectral distribution graph as a relative intensity as a hard number which represents raw plant usable energy within the total PAR and three peak absorption regions.

What I particularly like about the data shown in these charts is that it gives everyone an opportunity to see just how much energy is being emitted in the C (visible) region as compared to the lamps total output. I will leave you to your own conclusions...
 

captainmorgan

Well-Known Member
You don't need an integrating sphere to develop V-C-F. These values are achieved by knowing the lamps spectral distribution and factoring consumed watts verses it's efficiencies into turning electricity into plant usable light.

As a grow lamp mfg I might use an integrating sphere to easily determine PPF output. For general area lamp applications I would use it to determine a lamps lumen output. As an area light fixture mfg I would want an in situ value in lux/footcandles.

As a grow light fixture mfg I would not be interested in sphere data since they are photopically corrected for human visual luminosity function. The area readings that a sphere gives you are designed for candela plot plans and are photopically adjusted. Furthermore they are providing intensity not spectrum in a numerical value. With plants you would want to know those intensity values in the 3 peak absorption regions and totaled as a PPF/s value which can be accomplished mathematically.
I just love this shit,I may not understand much of it but I still love it.
 
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